At this moment, how could it possibly let Emiya Shirou think quietly?
Having lived for a thousand years, Black Zetsu knew what to do. When a person is impacted by information they cannot accept, it's very easy for them to let their imagination run wild and even think of some world-destroying conspiracy. At that point, no matter what corroborating information they receive, the conspiracy might linger in their mind.
Black Zetsu knew very well that it did have a world-destroying conspiracy.
Especially since Shirou was from the ancient era and already knew many things. If he were allowed to let his imagination run wild, he might just guess the truth about Kaguya's disappearance. It had to take this opportunity to instill its own ideas into him, to make him accept its identity calmly, to have him completely brainwashed by the so-called truth it was about to tell.
"Hear me out."
Black Zetsu felt the words were a bit familiar. Indeed, Shirou seemed to have just said the same thing. It felt this was truly a cycle of fate. It had no choice but to learn from his example and began to tell its own slightly fabricated and embellished story.
"In our era, you must have heard the story of the God Tree. In ancient times, it appeared in this world and became the faith of humanity. And Kaguya, who descended along with it, became the Rabbit Goddess of human faith. But what you don't know is that the humans of that era were also constantly fighting."
Black Zetsu exerted its brain, trying hard to make its mother appear in a more positive light. "The suffering humans prayed to Kaguya to quell the wars. Kaguya heard their prayers and used the power of the God Tree to pacify the wars of that era. However, this was not the end. Even though she possessed god-like power, even though her power was as strong as your wisdom in human research, she finally encountered a helpless dilemma."
It had not wasted its time. It had learned some communication techniques, like casually pulling Shirou into the story to evoke his empathy.
"Could it be..." Shirou frowned and began to think.
"That's right. There are too many humans in the world." Black Zetsu didn't wait for him to give the answer and quickly continued. "Kaguya hoped to distribute her power—the chakra in her body—to find some people with noble character like you, to have them help save the suffering world."
"Me?" Shirou shook his head, unwilling to accept the praise. "I don't have such a noble character. I am just a lucky person who was fortunate enough to obtain the power of the God Tree's remnants. I just don't want to fail this power, so I want to save the suffering world just like the Rabbit Goddess."
"Don't be modest," Black Zetsu resolutely refused to let him decline. "I have walked this world for a thousand years and have never seen even a sliver of your shadow again. In this world, people like you are too rare."
It sighed and continued the story. "However, Kaguya knew the influence of chakra was too powerful. She believed it could not be given to people casually, to avoid it being used for evil. Naturally, humans with noble character are always rare. Therefore, her plan was not very smooth. But this was no big deal for her. She had a long lifespan and enough time to find people to whom she could entrust chakra."
"Indeed, one should be cautious," Shirou nodded, seeming to strongly agree with the Kaguya in Black Zetsu's story.
"Yes," Black Zetsu sighed faintly. "But Kaguya's two sons did not think so."
"Two sons!" Shirou seemed to have heard a completely new version.
"That's right!" its voice turned sinister. "Besides the Sage of Six Paths, Hagoromo Otsutsuki, whom we know, Kaguya had another son, Hamura Otsutsuki. Because they had chakra since birth, they did not think it was a precious power. They thought their mother should proactively distribute it to the world and then guide people to decide their own destinies."
Black Zetsu was very subtle. It did not say too many bad things about the Sage, because he and Shirou were from the same era. However, it knew its words were enough to arouse Shirou's dissatisfaction.
"This..." Shirou's brow furrowed again. "To rashly distribute a power that can harm the world, this idea is a bit naive."
"Yes," Black Zetsu nodded. "And now we have seen the result. This naive idea was naturally rejected by Kaguya. She was stronger than anyone and lived longer than anyone. Her excellent insight and broad vision were enough for her to foresee the results we see today."
Rabbit Goddess? Excellent insight, broad vision?
Shirou was a bit suspicious that Black Zetsu was adding too much of its own bias. However, he would not expose it at this time and even had to show a look of admiration. "No wonder the people of our era would never forget the God Tree and the Rabbit Goddess."
Black Zetsu was a bit embarrassed to respond and could only continue. "Regrettably, the naive sons could not understand their mother's greatness. Kaguya, who had always been revered, rarely communicated with people and did not know how to make her two sons obey. Especially her excessive doting on them made her lack a mother's authority. The naive sons thought they knew better how to save the suffering world. Using the power their mother had given them, they started a war against her."
"That great catastrophe that almost destroyed the world?" Shirou's face suddenly changed. In ancient times, people had experienced a great catastrophe. Even when he transmigrated to this world, he had heard people's fear of it.
"That's right," Black Zetsu nodded, throwing the blame onto the Hagoromo brothers. "That was a war that almost destroyed the world. The two brothers had never realized how terrifying the power of chakra could be when truly unleashed. A single strike could kill countless humans. That was a true catastrophe. This is also the reason why Kaguya did not want the power of chakra to spread. When humans obtain it, they will inevitably use it to fight for benefits, which will only cause more suffering."
"Kaguya originally did not want to use power to defeat her own sons, but she saw this world almost being destroyed, saw those who believed in her die in the aftershocks. It was a painful thing for her. Those people whose homes were destroyed, those innocent people who died, plus the fact that the ones opposing her were her two most beloved sons... The Rabbit Goddess's heart finally softened. As a mother, she chose to back down."
Black Zetsu paused, looking at Shirou, who was engrossed in the story. It nodded with satisfaction and then continued with the end.
"In the end, the war ended. Kaguya, who was originally stronger, was sealed by her own sons." It made another excuse for the brothers while pinning more blame on them. "Because their lifespans were limited, they were worried that their mother would take back the distributed chakra after they died. From then on, the Rabbit Goddess disappeared."